The present invention pertains to duplicated processor configurations and more particularly to an arrangement for testing a standby processor in an active/standby duplex processor configuration.
Public policy requires that telecommunication systems provide 24 hour noninterrupted service to its subscribers. In order to achieve this end, telecommunication systems typically employ multiple processors, each processor capable of sustaining the system's functions. Many of these telecommunication systems were controlled by several large processors which normally executed their program in lock step. That is, each processor executed the same instruction at the same time. Some of these lock step processor arrangements had a third party processor which compared the execution of the two other processors to determine whether these processors where executing the same instruction at the same time. In addition, for detection of mismatches of the other processors, a third party processor would determine which processor is faulty and remove it from the configuration. Processors in such a telecommunication system were all on-line, active and operational until one processor was put off-line for a fault detection. Subsequently, any faulty processor was tested and verified before being placed back on-line, active and in service.
Other telecommunication systems include processor configurations with duplicated processors operating in a standby/active configuration. That is, one processor is active and operates both duplex copies of the system's peripherals until a fault is detected. Thereafter, the faulty processor is removed from service and the previously off-line, standby processor is put active and in service. The new active processor controls both copies of all system peripherals. As a result, an off-line processor maybe put into service without having suitable diagnostic testing performed just prior to its being placed in service.
Therefore, for telecommunication system operation it is insufficient for the system to simply switch over from one processor copy to the other without suitable prior diagnostic testing of the processor copy which is being put into active service.